The present invention relates to a defect inspection method for inspecting a minute defect existing on a sample surface and a defect inspection apparatus therefor.
In production lines of semiconductor substrates, thin film substrates, etc., in order to maintain and improve the yield of a product, inspection of a defect that may exist on the surface of semiconductor substrates, thin film substrates, etc. is performed. As conventional technologies, JP-A-Hei9 (1997)-304289 (patent document 1) and JP-A-2000-162141 (patent document 2) are known. In order to detect a minute defect, a laser beam focused to a few tens μm is irradiated thereon and scattered light from the defect is converged and detected.
In connection with rapid miniaturization of LSI wiring in recent years, the size of a defect that should be detected is approaching a detection limit of optical inspection. According to the semiconductor load map, mass production of LSI of a 36-nm node is going to be started in 2011, and a capability of detecting the defect having a size of about a half of DRAM 1/2 pitch is considered required. It is known that a magnitude l of scattered light occurring when the defect is illuminated by a laser has a relation of l∝d6, where d denotes a particle size of the defect. That is, when the defect size becomes small, the scattered light occurring thereby will decrease rapidly. Although, as methods of increasing the scattered light occurring, there exist wavelength shortening of illumination wavelength, power increasing of a laser, reduction of a laser illumination spot, etc., any of these methods comes with a possibility of giving damage to the sample due to an increase of temperature of an irradiated portion.